///////////////////////////////////////////////////////////////////////////////////
/// OpenGL Mathematics (glm.g-truc.net)
///
/// Copyright (c) 2005 - 2015 G-Truc Creation (www.g-truc.net)
/// Permission is hereby granted, free of charge, to any person obtaining a copy
/// of this software and associated documentation files (the "Software"), to deal
/// in the Software without restriction, including without limitation the rights
/// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
/// copies of the Software, and to permit persons to whom the Software is
/// furnished to do so, subject to the following conditions:
/// 
/// The above copyright notice and this permission notice shall be included in
/// all copies or substantial portions of the Software.
/// 
/// Restrictions:
///		By making use of the Software for military purposes, you choose to make
///		a Bunny unhappy.
/// 
/// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
/// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
/// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
/// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
/// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
/// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
/// THE SOFTWARE.
///
/// @ref gtc_ulp
/// @file glm/gtc/ulp.inl
/// @date 2011-03-07 / 2012-04-07
/// @author Christophe Riccio
///////////////////////////////////////////////////////////////////////////////////
/// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
///
/// Developed at SunPro, a Sun Microsystems, Inc. business.
/// Permission to use, copy, modify, and distribute this
/// software is freely granted, provided that this notice
/// is preserved.
///////////////////////////////////////////////////////////////////////////////////

#include "../detail/type_int.hpp"
#include <cmath>
#include <cfloat>
#include <limits>

#if(GLM_COMPILER & GLM_COMPILER_VC)
#	pragma warning(push)
#	pragma warning(disable : 4127)
#endif

typedef union {
    float value;
    /* FIXME: Assumes 32 bit int.  */
    unsigned int word;
} ieee_float_shape_type;

typedef union {
    double value;
    struct {
        glm::detail::int32 lsw;
        glm::detail::int32 msw;
    } parts;
} ieee_double_shape_type;

#define GLM_EXTRACT_WORDS(ix0, ix1, d)        \
    do {                                    \
        ieee_double_shape_type ew_u;        \
        ew_u.value = (d);                    \
        (ix0) = ew_u.parts.msw;                \
        (ix1) = ew_u.parts.lsw;                \
    } while (0)

#define GLM_GET_FLOAT_WORD(i, d)                \
    do {                                    \
        ieee_float_shape_type gf_u;            \
        gf_u.value = (d);                    \
        (i) = gf_u.word;                    \
    } while (0)

#define GLM_SET_FLOAT_WORD(d, i)                \
    do {                                    \
        ieee_float_shape_type sf_u;            \
        sf_u.word = (i);                    \
        (d) = sf_u.value;                    \
    } while (0)

#define GLM_INSERT_WORDS(d, ix0, ix1)            \
    do {                                    \
        ieee_double_shape_type iw_u;        \
        iw_u.parts.msw = (ix0);                \
        iw_u.parts.lsw = (ix1);                \
        (d) = iw_u.value;                    \
    } while (0)

namespace glm {
    namespace detail {
        GLM_FUNC_QUALIFIER float nextafterf(float x, float y) {
            volatile float t;
            glm::detail::int32 hx, hy, ix, iy;

            GLM_GET_FLOAT_WORD(hx, x);
            GLM_GET_FLOAT_WORD(hy, y);
            ix = hx & 0x7fffffff;        // |x|
            iy = hy & 0x7fffffff;        // |y|

            if ((ix > 0x7f800000) ||    // x is nan
                (iy > 0x7f800000))    // y is nan
                return x + y;
            if (x == y) return y;        // x=y, return y
            if (ix == 0) {                // x == 0
                GLM_SET_FLOAT_WORD(x, (hy & 0x80000000) | 1);// return +-minsubnormal
                t = x * x;
                if (t == x) return t; else return x;    // raise underflow flag
            }
            if (hx >= 0) {                // x > 0
                if (hx > hy) {            // x > y, x -= ulp
                    hx -= 1;
                } else {            // x < y, x += ulp
                    hx += 1;
                }
            } else {                // x < 0
                if (hy >= 0 || hx > hy) {    // x < y, x -= ulp
                    hx -= 1;
                } else {            // x > y, x += ulp
                    hx += 1;
                }
            }
            hy = hx & 0x7f800000;
            if (hy >= 0x7f800000) return x + x;  // overflow
            if (hy < 0x00800000) {             // underflow
                t = x * x;
                if (t != x) {          // raise underflow flag
                    GLM_SET_FLOAT_WORD(y, hx);
                    return y;
                }
            }
            GLM_SET_FLOAT_WORD(x, hx);
            return x;
        }

        GLM_FUNC_QUALIFIER double nextafter(double x, double y) {
            volatile double t;
            glm::detail::int32 hx, hy, ix, iy;
            glm::detail::uint32 lx, ly;

            GLM_EXTRACT_WORDS(hx, lx, x);
            GLM_EXTRACT_WORDS(hy, ly, y);
            ix = hx & 0x7fffffff;             // |x|
            iy = hy & 0x7fffffff;             // |y|

            if (((ix >= 0x7ff00000) && ((ix - 0x7ff00000) | lx) != 0) ||   // x is nan
                ((iy >= 0x7ff00000) && ((iy - 0x7ff00000) | ly) != 0))     // y is nan
                return x + y;
            if (x == y) return y;              // x=y, return y
            if ((ix | lx) == 0) {                        // x == 0
                GLM_INSERT_WORDS(x, hy & 0x80000000, 1);    // return +-minsubnormal
                t = x * x;
                if (t == x) return t; else return x;   // raise underflow flag
            }
            if (hx >= 0) {                             // x > 0
                if (hx > hy || ((hx == hy) && (lx > ly))) {    // x > y, x -= ulp
                    if (lx == 0) hx -= 1;
                    lx -= 1;
                } else {                            // x < y, x += ulp
                    lx += 1;
                    if (lx == 0) hx += 1;
                }
            } else {                                // x < 0
                if (hy >= 0 || hx > hy || ((hx == hy) && (lx > ly))) {// x < y, x -= ulp
                    if (lx == 0) hx -= 1;
                    lx -= 1;
                } else {                            // x > y, x += ulp
                    lx += 1;
                    if (lx == 0) hx += 1;
                }
            }
            hy = hx & 0x7ff00000;
            if (hy >= 0x7ff00000) return x + x;  // overflow
            if (hy < 0x00100000) {             // underflow
                t = x * x;
                if (t != x) {          // raise underflow flag
                    GLM_INSERT_WORDS(y, hx, lx);
                    return y;
                }
            }
            GLM_INSERT_WORDS(x, hx, lx);
            return x;
        }
    }//namespace detail
}//namespace glm

#if(GLM_COMPILER & GLM_COMPILER_VC)
#	pragma warning(pop)
#endif

namespace glm {
    template<>
    GLM_FUNC_QUALIFIER float next_float(float const &x) {
#		if GLM_HAS_CXX11_STL
        return std::nextafter(x, std::numeric_limits<float>::max());
#		elif((GLM_COMPILER & GLM_COMPILER_VC) || ((GLM_COMPILER & GLM_COMPILER_INTEL) && (GLM_PLATFORM & GLM_PLATFORM_WINDOWS)))
        return detail::nextafterf(x, FLT_MAX);
#		elif(GLM_PLATFORM & GLM_PLATFORM_ANDROID)
        return __builtin_nextafterf(x, FLT_MAX);
#		else
        return nextafterf(x, FLT_MAX);
#		endif
    }

    template<>
    GLM_FUNC_QUALIFIER double next_float(double const &x) {
#		if GLM_HAS_CXX11_STL
        return std::nextafter(x, std::numeric_limits<double>::max());
#		elif((GLM_COMPILER & GLM_COMPILER_VC) || ((GLM_COMPILER & GLM_COMPILER_INTEL) && (GLM_PLATFORM & GLM_PLATFORM_WINDOWS)))
        return detail::nextafter(x, std::numeric_limits<double>::max());
#		elif(GLM_PLATFORM & GLM_PLATFORM_ANDROID)
        return __builtin_nextafter(x, FLT_MAX);
#		else
        return nextafter(x, DBL_MAX);
#		endif
    }

    template<typename T, precision P, template<typename, precision> class vecType>
    GLM_FUNC_QUALIFIER vecType<T, P> next_float(vecType<T, P> const &x) {
        vecType<T, P> Result(uninitialize);
        for (detail::component_count_t i = 0; i < detail::component_count(Result); ++i)
            Result[i] = next_float(x[i]);
        return Result;
    }

    GLM_FUNC_QUALIFIER float prev_float(float const &x) {
#		if GLM_HAS_CXX11_STL
        return std::nextafter(x, std::numeric_limits<float>::min());
#		elif((GLM_COMPILER & GLM_COMPILER_VC) || ((GLM_COMPILER & GLM_COMPILER_INTEL) && (GLM_PLATFORM & GLM_PLATFORM_WINDOWS)))
        return detail::nextafterf(x, FLT_MIN);
#		elif(GLM_PLATFORM & GLM_PLATFORM_ANDROID)
        return __builtin_nextafterf(x, FLT_MIN);
#		else
        return nextafterf(x, FLT_MIN);
#		endif
    }

    GLM_FUNC_QUALIFIER double prev_float(double const &x) {
#		if GLM_HAS_CXX11_STL
        return std::nextafter(x, std::numeric_limits<double>::min());
#		elif((GLM_COMPILER & GLM_COMPILER_VC) || ((GLM_COMPILER & GLM_COMPILER_INTEL) && (GLM_PLATFORM & GLM_PLATFORM_WINDOWS)))
        return _nextafter(x, DBL_MIN);
#		elif(GLM_PLATFORM & GLM_PLATFORM_ANDROID)
        return __builtin_nextafter(x, DBL_MIN);
#		else
        return nextafter(x, DBL_MIN);
#		endif
    }

    template<typename T, precision P, template<typename, precision> class vecType>
    GLM_FUNC_QUALIFIER vecType<T, P> prev_float(vecType<T, P> const &x) {
        vecType<T, P> Result(uninitialize);
        for (detail::component_count_t i = 0; i < detail::component_count(Result); ++i)
            Result[i] = prev_float(x[i]);
        return Result;
    }

    template<typename T>
    GLM_FUNC_QUALIFIER T next_float(T const &x, uint const &ulps) {
        T temp = x;
        for (uint i = 0; i < ulps; ++i)
            temp = next_float(temp);
        return temp;
    }

    template<typename T, precision P, template<typename, precision> class vecType>
    GLM_FUNC_QUALIFIER vecType<T, P>
    next_float(vecType<T, P> const &x, vecType<uint, P> const &ulps) {
        vecType<T, P> Result(uninitialize);
        for (detail::component_count_t i = 0; i < detail::component_count(Result); ++i)
            Result[i] = next_float(x[i], ulps[i]);
        return Result;
    }

    template<typename T>
    GLM_FUNC_QUALIFIER T prev_float(T const &x, uint const &ulps) {
        T temp = x;
        for (uint i = 0; i < ulps; ++i)
            temp = prev_float(temp);
        return temp;
    }

    template<typename T, precision P, template<typename, precision> class vecType>
    GLM_FUNC_QUALIFIER vecType<T, P>
    prev_float(vecType<T, P> const &x, vecType<uint, P> const &ulps) {
        vecType<T, P> Result(uninitialize);
        for (detail::component_count_t i = 0; i < detail::component_count(Result); ++i)
            Result[i] = prev_float(x[i], ulps[i]);
        return Result;
    }

    template<typename T>
    GLM_FUNC_QUALIFIER uint float_distance(T const &x, T const &y) {
        uint ulp = 0;

        if (x < y) {
            T temp = x;
            while (temp != y)// && ulp < std::numeric_limits<std::size_t>::max())
            {
                ++ulp;
                temp = next_float(temp);
            }
        } else if (y < x) {
            T temp = y;
            while (temp != x)// && ulp < std::numeric_limits<std::size_t>::max())
            {
                ++ulp;
                temp = next_float(temp);
            }
        } else // ==
        {

        }

        return ulp;
    }

    template<typename T, precision P, template<typename, precision> class vecType>
    GLM_FUNC_QUALIFIER vecType<uint, P>
    float_distance(vecType<T, P> const &x, vecType<T, P> const &y) {
        vecType<uint, P> Result(uninitialize);
        for (detail::component_count_t i = 0; i < detail::component_count(Result); ++i)
            Result[i] = float_distance(x[i], y[i]);
        return Result;
    }
}//namespace glm
